Variable cam timing (VCT) is used in engines to advance or retard intake and/or exhaust valve timing. Consequently, intake and/or exhaust valve timing may be adjusted based on engine operating conditions to increase combustion efficiency and decrease emissions, if desired. Additionally, engine power output may be increased across a wider range of engine operating conditions.
Locking mechanisms in VCT systems have been developed to lock the VCT system in a desired base configuration when there is insufficient oil pressure to operate the VCT system, such as during engine startup. Backlash, or a gap between components of the locking mechanism, are controlled to tight specifications. If this backlash is too tight sticking and binding issues may occur between locking components and if this backlash is too large it may lead to noise, vibration, and harshness (NVH) issues. Methods for setting a locking pin backlash for the locking mechanism includes either adjusting the backlash during a VCT actuator assembly process or controlling it within tightly controlled tolerances. However, as one example, controlling the backlash in the way during assembly may involve precise measurement techniques that require frequent re-calibration. This may increase the time and cost of assembly.
One example approach for a phase control apparatus is shown by Moetakef et al. in U.S. Pat. No. 9,021,998. Therein, a phase control apparatus is discloses that includes a locking pin coupled to a vane of a rotor, the locking pin extending into a locking pin recess disposed in a cover plate in a locked configuration. There is a locking pin backlash between the locking pin and locking pin recess, as well as VCT overtravel (e.g., an additional gap) disposed between the vane and housing of the phase control apparatus. Thus, in the locked configuration, a gap exists between the vane including the locking pin and the housing.
The inventors herein have recognized potential issues with such systems. As one example, due to the VCT overtravel disclosed above, when the locking pin is moved into the recess to locking the phase control apparatus, the vane may travel too far towards the housing and result in component wear between the locking pin and side of the locking pin recess as the locking pin extends into the locking pin recess. This may result in degradation of the components of the phase control apparatus over time and increased NVH issues. Additionally, assembly of such a phase control apparatus may be more difficult due to having to maintain the VCT backlash between the locking pin and locking pin recess and the VCT overtravel gap between the vane and housing.
In one example, the issues described above may be addressed by a method for assembling a phase control apparatus for an engine camshaft, comprising: positioning a vane of a rotor against a housing of a drive wheel of the phase control apparatus; positioning a locking pin of the vane against a first side of a recess disposed in a cover plate of the phase control apparatus; and maintaining a backlash gap between only the locking pin and a second side of the recess. In this way, a backlash gap (or VCT overtravel) may be eliminated between the vane of the rotor and the housing and only included between the locking pin and the second side or the recess, thereby increasing the ease of assembly and reducing component wear between the locking pin and the recess.
As one example, during engine operation, when a request is received to lock the phase control apparatus of the VCT system, a rotor of the phase control apparatus is rotated into a retarded cam position where a first surface of a vane of the rotor is in face-sharing contact with a first surface of a housing of the phase control apparatus. A locking pin of the vane of the rotor is then extended into a locking pin recess disposed within a cover plate coupled to a housing of the phase control apparatus. In the locked configuration, while the first surface of the vane is in face-sharing contact with the first surface of the housing, a first side of the locking pin is contacting a first side of the recess and a second side of the locking pin is spaced away from a second side of the recess, the first side of the recess arranged proximate to the first surface of the housing. Further, while in the locked configuration the locking pin may move within the recess. However, a gap between the first side of the recess and the locking pin may remain the same as a gap between the first surface of the vane and the first surface of the housing, even as the locking pin moves within the recess. This configuration of the phase control apparatus allows for easier locking of the apparatus during engine operation and reduced wear between the locking pin and locking pin recess. As a result, a longevity of the phase control apparatus may be increased and NVH issues due to component wear may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
FIGS. 3-9B are drawn approximately to scale, however other relative dimensions may be used if desired.